Mainspring slipping ring for a self-winding timepiece



Sept. 9, 1969 J. H A'UETER 3,465,514

MAINSPRING SLIPPING RING FOR A SELF-WINDING TIMEPIECE Filed Jan. 2, 1968//YV/WOR Jean HAl/[TER Alforney United States Patent O Int. 01. G04b1/16 U.S. Cl. 58-86 2 Claims ABSTRACT OF THE DISCLOSURE A mainspring fora self-winding timepiece of the type including a barrel comprising, ablade, the blade being extended at its outer extremity to provide an endportion of increased thickness, said end portion being integral with theblade and adapted to bear against the inner wall of the barrel in themanner of a slipping ring.

BACKGROUND OF THE INVENTION Field of the invention Mainsprings forself-winding timepieces.

Description of the prior art In self-Winding watches of the prior art,the outer extremity of the mainspring is generally not rigidly securedto the barrel, as in the conventional watches, but is connected to thebarrel through the intermediary of a supplementary elastic blade, calleda slipping spring, arranged in such a manner as to bear elasticallyagainst the inner wall of the barrel. This slipping spring does not moverelatively to the barrel so long as the winding of the mainspring islower than a determined value. When this winding value of the mainspringis reached, the slipping spring slips on the inner wall of the barrel,thereby preventing any overwinding of the mainspring even when theautomatic Winding continues to operate.

The slipping spring is secured to the extremity of the outer coils ofthe mainspring by rivets or, more generally, by points of electricwelding. The assembling and the securing of the slipping spring to themainspring are delicate, due to the fact that the longitudinal axes ofthe mainspring and of the slipping spring must be in very precisealignment. Moreover, the rivets or the welding break away, therebyrendering the watch unusable.

SUMMARY OF THE INVENTION A primary object of the present invention is toremedy the drawbacks of the prior art.

The mainspring according to the invention is characterized by the factthat its blade is extended, at its outer extremity, by an integralportion of greater thickness, intended to be applied against the innerwall of the barrel in which the mainspring is located and to act as aslipping spring.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a barrel andmainspring for a self-winding watch, and embodying one form of theinvention;

FIG. 2 is an enlarged, fragmentary, broken perspective view of the outerextremity of the mainspring contained in the barrel represented in FIG.1, and

FIG. 3 is an enlarged, fragmentary, broken plan view of a modificationof a mainspring embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The barrel represented in FIG.1 is designated by 1aand contains a mainspring 2, the inner coil ofwhich is hooked to a core 3 and the outer extremity of which is extendedby 3,465,514 Patented Sept. 9, 1969 a portion 2a of greater thicknessthan that of the main body portion or blade of the mainspring, butformed integrally therewith.

When the spring is not mounted in the barrel, the portion 2a is reversedwith respect to the winding direction of the mainspring, so that oncethe mainspring is in place in the barrel, it exerts on the inner wallthereof a pressure which depends from its thickness, the end portion 2aof the spring thus acting like a slipping spring.

The portion 2a of the spring is produced during the rolling of thespring, for instance by varying the distance between the two rollers ofthe rolling mill during the operation, by means of a servo mechanismsetting this distance according to the advance of the rolled strap.

The effect of this process is that the end portion 2aof the mainspring,constituting the slipping spring, is of slightly less height than theblade of the spring.

In the example represented in FIGS. 1 and 2, the thickness of theportion 2a of the mainspring is substantially double that of the mainbody or blade of the spring; in practise, the thickness of end portion2a will be about 1.3 to 2 times that of the blade. Of course, thisthickness is variable as desired. In the case of the spring of FIGS. 1and 2, the thickness of the portion 2a is constant throughout its wholelength. As seen in plan, this portion has substantially the shape of arectangle. However, this thickness could vary; for example, thethickness could increase from the free extremity of the portion 2atowards the middle part thereof, and then decrease from the middle partto the inner extremity where it connects to the main body portion orblade of the mainspring. In such an embodiment, the plan view of the endportion of the mainspring would have the general shape of a rhomb; suchan arrangement would reinforce, in the middle portion of the slippingspring, the force exerted by the slipping spring on the wall of thebarrel.

It is to be noted that, as soon as a rolling mill is arranged in such away as to produce end portions of variable thickness, it is possible touse the mill for obtaining springs, the blades of which are also ofvariable thickness. Such a construction is shown for the mainspring 4 ofFIG. 3, which is provided with an end portion 4a of greater height,constituting a slipping spring, the blade of which is itself of athickness which decreases from the inner extremity of the mainspringtowards its outer extremity.

I claim:

1. A mainspring for a self-winding timepiece of the type including abarrel comprising, a blade, the blade being extended at its outerextremity by an integral end portion of increased thickness, thethickness being constant throughout its length and being between 1.3 and2 times the thickness of the blade, the thickened end portion beingadapted to bear against the inner wall of the barrel in which the springis disposed for functioning as a slipping ring.

2. A mainspring according to claim 1, characterized by the fact that thethickness of its end portion acting as a slipping spring issubstantially the same throughout the whole length of the end portion.

References Cited UNITED STATES PATENTS 43,464 7/1864 Philippe 58-86FOREIGN PATENTS 1,496,479 9/1967 France.

1,828 7/1863 Great Britain.

RICHARD B. WILKINSON, Primary Examiner GEORGE H. MILLER, JR., AssistantExaminer

